and how about the allocation unit size inside Windows for the Repository Partition? Is veeam also creating small files on the repository or only the backup files which will be at least a few MB-TB so i should choose the max ntfs allocation unit size of 64kb??

I'm in doubt about a couple of things, Veeam suggests the backups I/O is normally between 256/512KB, that means the stripe size of my raid array, be RAID-10 or RAID-5 for example should be larger than 256KB, right? I would assume the bigger the better for sequential writes as well?

Windows then formats a NTFS partition by default at 4k cluster size, and allows it to be up to 64KB (can't do higher, perhaps REFS will do?), so I also believe I should have this set up to 64KB as definitely we would not have small files with Veeam backups.